or

=Arc tan sinhx

let y= arc tan sinhx

differentiating with respect to x,then

dy/dx=d(arc tan sinhx0/dx

dy/dx=d(arc tan sinhx)/d(sinhx) *d(sinhx0/dx

dy/dx=1/(1+sinhx)* coshx

dy/dx=coshx/cosh^2x=sechx

answer..